It is hypothesized that breakdown of specific metabolic steps in kidney cells is the main factor which limits viability of isolated preserved kidneys. The purpose of this project is to provide a quantitative basis for identifying the sequential limiting steps in critical metabolic pathways, preventing or bypassing them by adding needed substrates for optimal perfusion conditions; and relate these to compensatory hypertrophy in a single remaining kidney after unilateral nephrectomy or transplantation. Thoroughbred Beagle dogs will be used. Genetic data, specific ages, growth patterns, nutritional history, renal function, and kidney weight for age data are available. One kidney will be removed, cold perfused up to 96 hours and reimplanted with contralateral nephrectomy. Cellular metabolic pathways in renal cortex and medulla of the in situ and extirpated kidney will be studied prior to and at intervals during extracorporeal preservation. Sequential steps to be studied quantitatively in the metabolic "production lines" include: 1) energy reactions, e.g. respiration, glycolysis, hexose monophosphate shunt, gluconeogenesis, and adenine nucleotide balance; 2) protein synthesis, e.g. incorporation of H3-amino acids into polysomal material, ribosomal RNA and nuclear DNA polymerases, and effects of specific inhibitors of RNA synthesis; 3) cell destruction, e.g. protein- degrading enzymes, RNAase, DNAase and other lysosomal proteinases; 4) membrane-related systems, e.g. adenyl cyclase system (3,5 cyclic AMP), ATPase, and cytoplasmic redox potential; 5) ultrastructural correlates of the metabolic lesions. Limitations of substrate and/or enzyme- related failure to sustain specific metabolic steps in each of these systems will be identified. Preservation perfusate solutions then will be modified to sustain function of these systems. Following preservation, the isolated kidney will be reimplanted, the in situ kidney removed, perfused, and the sequence of studies repeated on both kidneys. The autotransplantation procedure should obviate rejections and use of immunosuppressive agents. Ultimately, the systems will be tested for preservation of human kidneys.